Lately I’ve been running into a warning in Firefox notifying me that a script on the current website was not responding and asking if I wanted to stop or continue. That’s a pretty vague warning and I was initially surprised by the cause. The strange thing was that the website seemed to have loaded completely and the warning was displayed despite this.
If you suspect that a script just needs a few more seconds to run, you should edit a setting in Firefox settings. Type about:config in the address bar and filter by the string dom.max_script_run_time. The default setting is 20 (seconds), just add a few more, increase to 25 for example, or even more.
There are a couple of other options available to resolve the script warnings in Firefox. For example, you can install a plugin like NoScript or YesScript to block all or only select scripts from running in the browser. Note that this works fine only if the script is not required for the functionality of the site.
Another option to find out if extensions are causing the warning message is to run Firefox with all extensions disabled. You can do this by clicking Firefox > Help > Restart with add-ons disabled.